Such nozzle heads are commonly used on spray devices for the hydrostatic, pneumatic or combined hydrostatic and pneumatic atomization of paints, varnishes, adhesives or other liquid substances, particularly in paint spray guns.
In the nozzle heads of such spray devices, the air ring nozzle has the function of discharging the compressed air supplied to the device in the form of a high-energy air jet that draws material from another central nozzle, atomizes this material and forms a spray jet containing said material. Horn air nozzles usually are directed at the spray jet obliquely and equidirectionally to the outflow direction in laterally arranged horns of the nozzle head that point forward in the spray jet direction such that the air jets being discharged from these nozzles can respectively deform or form the spray jet. Due to the lateral deformation/formation, a more or less large flat jet or flat jet and round jet is created in dependence on the flow energy (air quantity, air pressure, flow speed, etc.).
In order to achieve an optimal work result, the spray jet needs to be adapted, among other things, with respect to the jet width, the material distribution, the material type and the droplet size. The adaptation is essentially carried out in dependence on the physical boundary conditions (supply air pressure, air quantity, etc.) in the form of a constructive adaptation of the openings of the central air ring nozzle and the horn air nozzles. In order to achieve sufficiently homogenous spray jets, one, two, three or more horn air nozzles that interact with the central opening of the central nozzle are typically used per horn. Paint spray guns with one, two or more horn air nozzles are known from practical applications and ensure a sufficient jet formation and atomization based on the criteria mutual distance, diameter, angle and distance from the paint nozzle opening, as well as the number thereof. In this case, the horn air nozzles are arranged in an air cap that is mounted on the paint spray gun body, usually screwed thereon by means of mounting rings. The central air nozzle may also be directly screwed, clipped or similarly mounted on the paint nozzle or on the paint spray gun body. A nozzle head of this type is known, for example, from German Utility Model G 90 01 265.8. The paint nozzle openings and the horn air nozzle openings are conventionally realized in the form of round bores.
In practical applications, the diameters of the horn air nozzles are realized differently depending on the supply pressure and the individually desired shape of the spray jet. The effect of the individual horn air nozzles is dependent on the supply pressure. Splitting of the jet may occur at higher supply pressures. An undesirably coarse atomization with small jet width may occur at excessively low supply pressures. In addition, the material throughput and other material properties (e.g., viscosity, rheology, etc.) are also highly dependent on the supply pressure and the arrangement of the horn air nozzles. When using one or more smaller horn air nozzles or unfavorable bore angles, back-misting problems may occasionally arise on the opening surfaces of the nozzles due to the suction effect occurring at smaller nozzle or bore diameters.
Small control openings or auxiliary atomizer openings that contribute to the jet formation and the atomization are usually arranged around the central nozzle. In order to transform the pre-formed jet emerging from the cylindrical tube of the central air nozzle opening into a different shape or, for example, to convert a round jet into a flat jet, large amounts of energy from the jet formation bores and the horn bores are required, which ultimately lead to high energy losses and limit the jet formation.
One significant disadvantage of this jet formation method can be seen in that a large part of the energy for the jet formation and the post-atomization is already blown out into the surrounding air through the narrow bores and multiple outlets (large shear planes on the surface in connection with significant fluctuations in speed).
Modified nozzle heads with possibly deviating spraying parameters and geometries frequently need to be used for slightly different paint or varnish materials in order to achieve a flawless spray pattern and therefore the desired result of the paint application, varnish application or other material application.